Stabilized polymers of cyclic esters of hydroxycarboxylic acids

摘要

A polymer of a cyclic ester of a hydroxycarboxylic acid is stabilized against U.V. light by adding to it a phenolic compound containing two aromatic rings linked together by a carbonyl group, a carbonyloxy group or a group of three nitrogen atoms belonging to a 1,2,3-triazole configuration condensed with one of the aromatic rings. Instead of the phenols per se, their metal derivatives may be used, the metal preferably being nickel, cobalt, copper, manganese, tin, zinc or cadmium. Specified stabilizers are 4-tert.-butylphenyl salicylate, 4-n-dodecylphenyl salicylate, 2 - hydroxy - 4 - n - octoxybenzophenone, 2: 21 - dihydroxy - 4 - n - octoxy benzophenone and 2: 21 - dihydroxy - 4 - n - methoxybenzophenone; also the 2-tert.-butylphenyl ester, the 2: 6-di-tert.-butylphenyl ester and the 2: 4-di-tert.-butylphenyl ester of 3,5-di-tert. -butyl - 4 - hydroxybenzoic acid; also 2-(21 - hydroxyphenyl) benzotriazole, 2 - (21 - hydroxy - 51 - methylphenyl) benzotriazole, 2 - (21 - hydroxy - 5 - tert. - butylphenyl) benzotriazole, 2 - (21 - hydroxy - 51 - amylphenyl) benzotriazole, 2 - (21 - hydroxy - 51 - n - nonylphenyl) benzotriazole, 2 - (21 - hydroxy - 51-cyclohexyphenyl) benzotriazole, 2 - (21-hydroxy - 4 - carboxymethoxyphenyl) benzotriazole, 2 - (21 - hydroxy - 51 - carboxymethylphenyl) benzotriazole, 2 - (21,41 - dihydroxyphenyl) benzotriazole, 2 - (21,41 - dihydroxy - 51-chlorophenyl) benzotriazole, 2 - (21 - hydroxy-31, 51 - dimethylphenyl) - 5 - methyl - benzotriazole, 2 - (21 - hydroxy - 41 - n - octoxyphenyl) benzotriazole and 2-(21-hydroxy-51-n-octoxyphenyl) - benzotriazole. Additional stabilizers may also be added, e.g. phenyl-b -naphthylamine, 2: 6 - diisopropyl phenol, 2: 6 - di - tert.-butyl - 4 - methylphenol, 2: 2 - bis - (31,51 - di-tert. - butyl - 41 - hydroxyphenyl) propane, 1: 3: 5 - tris - (31,51 - di - tert. - butyl - 41/h - hydroxybenzyl) - 2: 4: 6 - trimethylbenzene, tetraalkyl thiuram disulphides, dilauryl-b -thiodipropionate and tri-(nonylphenyl) phosphite. The stabilizers may be added to the polyester in dry form or dissolved in a solvent (e.g. an aromatic hydrocarbon, an ether, an alcohol or a ketone), or alternatively the stabilizers may be added during the polymerization of the cyclic esters. An example describes the stabilization of a polyester of a ,a -dimethyl-b -propiolactone.